Transfer method of applying adhesive to substrates

ABSTRACT

A transfer adhesive sandwich includes a flexible carrier sheet having an adhesive layer releasably bonded to one surface and having an opposite surface to which the adhesive layer is releasably bondable with substantially less tenacity than the tenacity of the bond between the adhesive layer and the one surface. A plurality of the sandwiches are stacked on top of one another to form a pad from which individual sandwiches are strippable. When the adhesive layer is pressed against a substrate, it adheres to the substrate with a tenacity substantially greater than the tenacity of the bond between the adhesive layer and the one surface of the carrier sheet so that the carrier sheet can be stripped away to leave the adhesive layer on the substrate.

This application is a continuation of application Ser. No. 671,769,filed Nov. 15, 1984, abandoned.

BACKGROUND OF THE INVENTION

This invention relates to the art of adhesive laminates and to a methodof applying adhesive to a substrate. The laminate and method of thepresent invention are particularly adapted for use in attaching asubstrate framework to another member and will be described withspecific reference thereto. However, it will be appreciated that theinvention has broader aspects and may be used for other purposes in manydifferent environments.

Many devices are operated by electronic controls having manuallyoperable membrane or push-button switches which are accessible throughopenings in a substrate framework or face plate attached to the device.It is common to attach the framework or face plate with the use ofadhesive which is applied to the rear surface of the framework or faceplate. Properly applying adhesive to the rear surface of the frameworkrequires care so that the appearance of the device will not be marredand so that the framework will be securely attached against accidentaldisplacement. It would be desirable to have a simple and cleanarrangement for applying adhesive to frameworks of the type described.

SUMMARY OF THE INVENTION

A transfer adhesive sandwich includes a flexible carrier sheet having alayer of pressure-sensitive adhesive releasably bonded to one surfacethereof and having an opposite surface to which the adhesive layer isbondable with a tenacity substantially weaker than the tenacity of thebond between the adhesive layer and the one surface. A plurality of thesandwiches are stacked on top of one another to form a pad, with theadhesive layer on each sandwich engaging the opposite surface of acarrier sheet on an adjacent sandwich. The sandwiches are strippable oneby one from the pad.

In accordance with the present invention, the adhesive layer on asandwich is pressed into engagement with a substrate to which theadhesive layer bonds with a tenacity substantially greater than thetenacity of the bond between the adhesive layer and the one surface ofthe carrier sheet. Pulling on the carrier sheet then strips the sheetfrom the adhesive layer such that the adhesive layer remains bonded tothe substrate. The substrate can then be attached to or receive anotherdevice or base member through the use of the pressure-sensitive adhesivelayer.

The carrier sheet may comprise polyethylene or other suitable flexiblematerials. The opposite surface of the carrier sheet may be providedwith a release material so that the adhesive layer of one sandwich willadhere very lightly to the opposite surface of a carrier sheet on anadjacent sandwich for maintaining the integrity of the pad whileallowing easy stripping of individual sandwiches from the pad. Where thecarrier sheet is a material to which the adhesive layer does not readilyadhere, it may be unnecessary to provide a layer of release material onthe opposite surface thereof. In such a situation, the one surface ofthe carrier sheet may be suitably treated for enhancing the bond betweenthe adhesive layer and the one surface. Thus, the opposite surfaces ofthe carrier sheet have characteristics such that the adhesive layerbonds to one surface with a tenacity substantially greater than thetenacity to which it bonds to the opposite surface.

The carrier sheet preferably includes an outwardly extending tab whichis not coated with adhesive so that it can be readily grasped forpulling a sandwich from the pad, and for pulling a carrier sheet awayfrom the adhesive layer bonded to a substrate.

The adhesive layer is preferably applied to a carrier sheet in adiscontinuous pattern having a plurality of spaced-apart openingstherein surrounded by adhesive. The openings in the adhesive layercorrespond in size, shape, and spacing with openings through a substrateframework or face plate to be applied to a device having manuallyoperable membrane or push-button switches aligned with the openings.

One principal advantage of the present invention is the provision of anew transfer adhesive sandwich.

Another principal advantage of the invention resides in the provision ofa new method for applying pressure-sensitive adhesive to substrates.

A further advantage of the invention is the provision of a transferadhesive sandwich and method which make it very simple and economical toapply adhesive to substrate frameworks or the like.

Still other advantages and benefits of the invention will becomeapparent to those skilled in the art upon a reading and understanding ofthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in certain parts and arrangements of parts,a preferred embodiment of which will be described in detail in thisspecification and illustrated in the accompanying drawings which form apart hereof and wherein:

FIG. 1 is a top plan view of a transfer adhesive sandwich constructed inaccordance with the present invention;

FIG. 2 is a cross-sectional elevational view taken generally along lines2--2 of FIG. 1;

FIG. 3 is a side elevational view showing a plurality of the sandwichesof FIGS. 1 and 2 stacked on top of one another;

FIG. 4 is a rear plan view of a substrate framework having a pluralityof openings therein alignable with membrane or push-button sandwiches;

FIG. 5 is a view similar to FIG. 4 showing the sandwich of FIGS. 1 and 2positioned in engagement with the rear surface of the substrateframework;

FIG. 6 is an end elevational view taken generally in the direction oflines 6--6 of FIG. 5 and showing a carrier sheet being stripped from itsadhesive layer; and,

FIG. 7 is a rear plan view of the substrate framework of FIG. 4 with alayer of adhesive applied thereto following the procedures of FIGS. 5and 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein the showings are for purposes ofillustrating a preferred embodiment of the invention only and not forpurposes of limiting same, FIG. 1 shows a transfer adhesive sandwich Aconstructed in accordance with the present invention and including aflexible carrier sheet B having opposite planar surfaces 10, 12 (FIG.2).

A layer C of pressure-sensitive adhesive is releasably bonded to onesurface 10 of carrier sheet B. Opposite surface 12 of the carrier sheethas a layer of release material D thereon and to which adhesive layer Cis releasably bondable with a tenacity substantially weaker than thetenacity of the bond between adhesive layer C and one surface 10.

At least one tab 14 projects outwardly from carrier sheet B to begrasped for pulling on carrier sheet B and otherwise manipulating same.Tab 14 is completely free of any adhesive. Where carrier sheet B isgenerally rectangular in the manner shown in the FIGURES, tab 14projects generally diagonally outward from one corner thereof and is ofa size to accommodate easy grasping between a person's thumb and indexfinger. The intersections of the edges of tab 14 with the edges ofcarrier sheet B are preferably smoothly curved as shown in FIG. 1 toavoid stress concentrations. This, in turn, prevents tearing of carriersheet B when tab 14 is pulled to separate a sandwich from a pad, or toseparate a carrier sheet from its adhesive layer.

Pressure-sensitive adhesive layer C is applied to one surface 10 ofcarrier sheet B in a predetermined discontinuous pattern. Adhesive layerC has a continuous outer periphery 18 which is spaced inwardly from theouter periphery of carrier sheet B to leave a peripheral border 20 onone surface 10 which is free of adhesive. In the arrangement shown, thediscontinuous pattern of pressure-sensitive adhesive layer C is suchthat a plurality of spaced-apart openings 22 are provided therein. Asshown, openings 22 are generally square, and it will be recognized thatother shapes and patterns can be used to accommodate differentapplications or installations without in any way departing from theoverall intent or scope of the invention. Also, although six openings 22are shown in FIG. 1, it will be recognized that a greater or lessernumber of such openings can be provided, and that the openings can haveirregular spacings.

Openings 22 in adhesive layer C are completely surrounded by adhesive,and adhesive layer C has an outer border 24 which is substantially widerthan adhesive webs 26 between adjacent openings 22. In the arrangementshown, adhesive outer border 24 generally corresponds with the shape ofborder 20 on one surface 10 of carrier sheet B. However, it will berecognized that the peripheral shape of adhesive layer C may differ fromthat of carrier sheet B. When sandwich A is used for attacing asubstrate framework to a device having membrane or push-button switches,openings 22 are generally equidistantly spaced both horizontally andvertically.

It will be recognized that many different materials can be used forflexible carrier sheet B. In one arrangement, polyethylene plastic filmhas been used with excellent results. However, it will be recognized bythose skilled in the art that other materials compatible with theparticular adhesive and the particular application can be satisfactorilyemployed. When polyethylene has been used, the thickness of carriersheet B is approximately six mils, while the thickness ofpressure-sensitive adhesive layer C is approximately one mil and thethickness of release layer D, if provided, is approximately one-halfmil. In general, the thickness of carrier sheet B will be substantiallygreater than that of adhesive layer C which, in turn, will besubstantially greater than the thickness of release layer D. However,the degree by which the thickness of flexible carrier sheet B exceedsthe thickness of adhesive layer C will normally be many times that bywhich the thickness of adhesive layer C exceeds that of release layer D.

For certain materials and adhesives, it may be possible to omit releaselayer D as would be the case when carrier sheet B has surfacecharacteristics such that pressure-sensitive adhesive layer C will bondonly lightly to carrier sheet opposite surface 12. Under thesecircumstances, it may be desirable to treat carrier sheet one surface 10prior to application of adhesive layer C thereto so that such layer willbond to one surface 10 with a tenacity substantially greater than itwill bond to opposite surface 12. However, if adhesive layer C is hotwhen applied to one surface 10, it may bond thereto with a tenacitysubstantially greater than it will bond to opposite surface 12 whencold, and no treatment of either surface may be necessary. In any event,the sandwich is characterized by a carrier sheet having one surface towhich a pressure-sensitive adhesive layer is bonded with a tenacitysubstantially greater than the tenacity with which such adhesive layeris bondable to the opposite surface thereof. Although adhesive layer Chas openings 22 therein, it will be recognized and appreciated that,preferably, carrier sheet B is continuous.

FIG. 3 shows a pad E formed by a plurality of sandwiches A stacked inalignment on top of one another. For ease of illustrated, FIG. 3 showsonly a few sandwiches A on an enlarged scale, and pad E normally will becomprised of around twenty-five or more of these sandwiches. However, itis to be recognized that any number of sandwiches A could be included ina pad as may be necessary and/or desired. Sandwiches A are stacked ontop of one another with the adhesive layer C on one sandwich engagingand being releasably bonded to release layer or material D on theadjacent sandwich. Thus, the top sandwich A is strippable from the padby grasping tab 14 and pulling same as indicated in FIG. 3. In view ofthe fact that the tenacity of the bond between surface 10 of a carriersheet B and adhesive layer C is substantially greater than the tenacityof the bond between adhesive layer C and release layer D, an entiresandwich as described with respect to FIGS. 1 and 2 is strippable frompad E of FIG. 3. At the same time, there is some adhesion betweenpressure-sensitive adhesive layer C and release layer D for maintainingthe alignment and integrity of pad E. The bottom carrier sheet B in padE will not have an adhesive layer C applied thereto. In the alternative,it is possible to simply place a layer of release material or paper overadhesive layer C of the bottom sandwich.

FIG. 4 shows a substrate framework or face plate F having a plurality ofspaced-apart openings 30 therethrough generally corresponding in size,shape, and spacing to openings 22 in adhesive layer C on a sandwich B.Openings 22 in the adhesive layer are preferably somewhat larger in sizethan openings 30 so that alignment of adhesive layer C with the rearsurface of the substrate framework is not critical. Substrate frameworkF may be comprised of any suitable material such as metal, plastic,wood, paper or such which are painted or otherwise coated. The substrateframework will normally have a thickness which is substantially greaterthan the thickness of carrier sheet B and will be substantially rigid ascompared to the carrier sheet.

The surface characteristics of at least the rear surface of substrateframework F are also such that pressure-sensitive adhesive layer C willadhere thereto with a tenacity substantially greater than the tenacityof the bond between adhesive layer C and one surface 10 of a carriersheet B. As previously explained, openings 22 in adhesive layer C arepreferably somewhat larger than openings 30 in substrate framework F andadhesive webs 26 of adhesive layer C are also substantially narrowerthan the width of the webs between adjacent openings 30. Such anarrangement makes it possible to rapidly position a sandwich B on therear surface of substrate framework F with adhesive layer openings 22generally aligned with openings 30 and without having any adhesiveprojecting into openings 30. At the same time, the adhesive layer willcompletely surround each opening 30 in the substrate framework.

FIG. 5 shows a sandwich B after it has been stripped from pad E of FIG.3 and is being applied to the rear surface of a substrate framework F ofFIG. 4. Sandwich B is positioned with its pressure-sensitive adhesivelayer C engaging the rear surface of the substrate framework and withopenings 22 in adhesive layer C generally aligned with openings 30 insubstrate framework F.

Once carrier sheet B is pressed against the rear surface of substrateframework F, tab 14 is grasped and pulled away from the substrateframework in order to pull the flexible carrier sheet away from adhesivelayer C. The adhesive layer, in turn, remains bonded to substrateframework F as shown in FIG. 6. Once carrier sheet B is pulledcompletely away from adhesive layer C, the rear surface of substrateframework F appears as shown in FIG. 7 with adhesive layer C bondedthereto in surrounding relationship to openings 30. Substrate F may thenbe applied to another device or base member so that membrane orpush-button switches are aligned with openings 30. The device or basemember to which substrate framework F is applied may be of any knowntype such as a kitchen appliance in the form of a range or oven havingmembrane or push-button switches to operate an electronic control. Thesubstrate framework may also be applied to various industrial controlboxes, or to electronic calculators or the like.

In the subject invention, assembly of a plurality of sandwiches into apad prevents drying of the pressure-sensitive adhesive layer C until itis ready for use by stripping a sandwich from the pad. Also, the padeliminates the need for a separate release paper or the like on theexposed surface of each adhesive layer. In one form of the invention,the carrier sheet and the release layer (if required) are generallytransparent to accommodate ready alignment of the adhesive pattern withthe substrate pattern. Also, the adhesive is generally opaque so thatthe adhesive pattern may be clearly differentiated from the carriersheet. It is to be appreciated, however, that other arrangements couldalso be satisfactorily employed to facilitate ease of alignment. Forexample, the carrier sheets may include printed indicia or the likewhich are alignable with a selected area of an associated substrate sothat, in turn, the adhesive pattern will be properly aligned with thesubstrate pattern.

The specific chemical conformation of the adhesive material does notitself comprise a part of the present invention. However, depending uponthe intended application for the subject new transfer adhesive sandwich,it may be desirable to have the adhesive include certain physical and/orchemical characteristics. For example, the ability of the adhesive toconduct static electricity would be advantageous when the adhesivesandwich is to be used in association with membrane-type switch platesor the like. Also, a water-soluble adhesive would be advantageous foraccommodating soldering or the like. Still other capabilities for orcharacteristics of the adhesive material would be desirable as afunction of the specific use intended for the sandwiches.

The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon a reading and understanding of this specification. It isintended to include all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalentsthereof.

Having thus described the invention, it is now claimed:
 1. A method ofapplying adhesive to substrates having a plurality of spaced-apartopenings therein comprising the steps of:(a) providing a pad of adhesivesandwiches stacked on top of one another, each sandwich including aflexible carrier sheet having a pressure-sensitive adhesive layerreleasably bonded to one surface thereof in a predetermineddiscontinuous pattern including openings corresponding in size and shapeto the spaced-apart openings in said substrates and having an oppositesurface to which the adhesive layer is bondable with substantially lesstenacity than the tenacity with which the adhesive layer is bonded tothe one surface, said sandwiches being stacked on top of one anotherwith the adhesive layer on one sandwich releasably bonded to an oppositesurface of a carrier sheet on an adjacent sandwich; stripping a sandwichfrom said pad; (b) positioning the adhesive layer on the strippedsandwich against a one of said substrates; (c) pressing on the carriersheet of the stripped sandwich to bond its adhesive layer to thesubstrate with substantially greater tenacity than the tenacity of thebond between the adhesive layer and its carrier sheet; (d) pulling thecarrier sheet to strip same from its adhesive layer which remains bondedto the substrate; and, (e) repeating the steps of stripping, pressing,and pulling with each sandwich in the pad.
 2. The method as defined inclaim 1 wherein said adhesive layer and said substrate have spaced-apartopenings therein of generally the same size and shape, and said step ofpositioning being carried out by aligning the openings in the adhesivelayer with the openings in the substrate.
 3. The method as defined inclaim 1 wherein each carrier sheet of each sandwich has an outwardlyextending tab which is free of adhesive, and said steps of stripping andpulling being carried out by grasping the tab.
 4. A method of applyingadhesive to a substrate comprising the steps of: providing a flexiblecarrier sheet having a pressure-sensitive adhesive layer releasablybonded to one surface thereof in a predetermined discontinuous patterncorresponding to the desired application of adhesive to the substrate;placing said adhesive layer against the substrate and pressing on saidsheet to bond said adhesive layer to the substrate with a tenacitysubstantially greater than the tenacity of the bond between said carriersheet and said adhesive layer; and, pulling said carrier sheet and saidsubstrate to strip said carrier sheet from said adhesive layer whichremains bonded to said substrate; and, wherein said substrate has aplurality of spaced-apart openings therethrough and said predetermineddiscontinuous pattern of said adhesive layer has spaced-apartcorresponding openings therein, and said step of placing said adhesivelayer against said substrate is carried out by aligning said openings insaid adhesive layer with said openings in said substrate.